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diff --git a/v_windows/v/old/vlib/rand/sys/system_rng.c.v b/v_windows/v/old/vlib/rand/sys/system_rng.c.v
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+++ b/v_windows/v/old/vlib/rand/sys/system_rng.c.v
@@ -0,0 +1,275 @@
+// Copyright (c) 2019-2021 Alexander Medvednikov. All rights reserved.
+// Use of this source code is governed by an MIT license
+// that can be found in the LICENSE file.
+module sys
+
+import math.bits
+import rand.seed
+import rand.constants
+
+// Implementation note:
+// ====================
+// C.rand returns a pseudorandom integer from 0 (inclusive) to C.RAND_MAX (exclusive)
+// C.rand() is okay to use within its defined range.
+// (See: https://web.archive.org/web/20180801210127/http://eternallyconfuzzled.com/arts/jsw_art_rand.aspx)
+// The problem is, this value varies with the libc implementation. On windows,
+// for example, RAND_MAX is usually a measly 32767, whereas on (newer) linux it's generally
+// 2147483647. The repetition period also varies wildly. In order to provide more entropy
+// without altering the underlying algorithm too much, this implementation simply
+// requests for more random bits until the necessary width for the integers is achieved.
+const (
+	rand_limit     = u64(C.RAND_MAX)
+	rand_bitsize   = bits.len_64(rand_limit)
+	u32_iter_count = calculate_iterations_for(32)
+	u64_iter_count = calculate_iterations_for(64)
+)
+
+fn calculate_iterations_for(bits int) int {
+	base := bits / sys.rand_bitsize
+	extra := if bits % sys.rand_bitsize == 0 { 0 } else { 1 }
+	return base + extra
+}
+
+// SysRNG is the PRNG provided by default in the libc implementiation that V uses.
+pub struct SysRNG {
+mut:
+	seed u32 = seed.time_seed_32()
+}
+
+// r.seed() sets the seed of the accepting SysRNG to the given data.
+pub fn (mut r SysRNG) seed(seed_data []u32) {
+	if seed_data.len != 1 {
+		eprintln('SysRNG needs one 32-bit unsigned integer as the seed.')
+		exit(1)
+	}
+	r.seed = seed_data[0]
+	C.srand(r.seed)
+}
+
+// r.default_rand() exposes the default behavior of the system's RNG
+// (equivalent to calling C.rand()). Recommended for testing/comparison
+// b/w V and other languages using libc and not for regular use.
+// This is also a one-off feature of SysRNG, similar to the global seed
+// situation. Other generators will not have this.
+[inline]
+pub fn (r SysRNG) default_rand() int {
+	return C.rand()
+}
+
+// r.u32() returns a pseudorandom u32 value less than 2^32
+[inline]
+pub fn (r SysRNG) u32() u32 {
+	mut result := u32(C.rand())
+	for i in 1 .. sys.u32_iter_count {
+		result = result ^ (u32(C.rand()) << (sys.rand_bitsize * i))
+	}
+	return result
+}
+
+// r.u64() returns a pseudorandom u64 value less than 2^64
+[inline]
+pub fn (r SysRNG) u64() u64 {
+	mut result := u64(C.rand())
+	for i in 1 .. sys.u64_iter_count {
+		result = result ^ (u64(C.rand()) << (sys.rand_bitsize * i))
+	}
+	return result
+}
+
+// r.u32n(max) returns a pseudorandom u32 value that is guaranteed to be less than max
+[inline]
+pub fn (r SysRNG) u32n(max u32) u32 {
+	if max == 0 {
+		eprintln('max must be positive integer')
+		exit(1)
+	}
+	// Owing to the pigeon-hole principle, we can't simply do
+	// val := rng.u32() % max.
+	// It'll wreck the properties of the distribution unless
+	// max evenly divides 2^32. So we divide evenly to
+	// the closest power of two. Then we loop until we find
+	// an int in the required range
+	bit_len := bits.len_32(max)
+	if bit_len == 32 {
+		for {
+			value := r.u32()
+			if value < max {
+				return value
+			}
+		}
+	} else {
+		mask := (u32(1) << (bit_len + 1)) - 1
+		for {
+			value := r.u32() & mask
+			if value < max {
+				return value
+			}
+		}
+	}
+	return u32(0)
+}
+
+// r.u64n(max) returns a pseudorandom u64 value that is guaranteed to be less than max
+[inline]
+pub fn (r SysRNG) u64n(max u64) u64 {
+	if max == 0 {
+		eprintln('max must be positive integer')
+		exit(1)
+	}
+	// Similar procedure for u64s
+	bit_len := bits.len_64(max)
+	if bit_len == 64 {
+		for {
+			value := r.u64()
+			if value < max {
+				return value
+			}
+		}
+	} else {
+		mask := (u64(1) << (bit_len + 1)) - 1
+		for {
+			value := r.u64() & mask
+			if value < max {
+				return value
+			}
+		}
+	}
+	return u64(0)
+}
+
+// r.u32n(min, max) returns a pseudorandom u32 value that is guaranteed to be in [min, max)
+[inline]
+pub fn (r SysRNG) u32_in_range(min u32, max u32) u32 {
+	if max <= min {
+		eprintln('max must be greater than min')
+		exit(1)
+	}
+	return min + r.u32n(max - min)
+}
+
+// r.u64n(min, max) returns a pseudorandom u64 value that is guaranteed to be in [min, max)
+[inline]
+pub fn (r SysRNG) u64_in_range(min u64, max u64) u64 {
+	if max <= min {
+		eprintln('max must be greater than min')
+		exit(1)
+	}
+	return min + r.u64n(max - min)
+}
+
+// r.int() returns a pseudorandom 32-bit int (which may be negative)
+[inline]
+pub fn (r SysRNG) int() int {
+	return int(r.u32())
+}
+
+// r.i64() returns a pseudorandom 64-bit i64 (which may be negative)
+[inline]
+pub fn (r SysRNG) i64() i64 {
+	return i64(r.u64())
+}
+
+// r.int31() returns a pseudorandom 31-bit int which is non-negative
+[inline]
+pub fn (r SysRNG) int31() int {
+	return int(r.u32() & constants.u31_mask) // Set the 32nd bit to 0.
+}
+
+// r.int63() returns a pseudorandom 63-bit int which is non-negative
+[inline]
+pub fn (r SysRNG) int63() i64 {
+	return i64(r.u64() & constants.u63_mask) // Set the 64th bit to 0.
+}
+
+// r.intn(max) returns a pseudorandom int that lies in [0, max)
+[inline]
+pub fn (r SysRNG) intn(max int) int {
+	if max <= 0 {
+		eprintln('max has to be positive.')
+		exit(1)
+	}
+	return int(r.u32n(u32(max)))
+}
+
+// r.i64n(max) returns a pseudorandom i64 that lies in [0, max)
+[inline]
+pub fn (r SysRNG) i64n(max i64) i64 {
+	if max <= 0 {
+		eprintln('max has to be positive.')
+		exit(1)
+	}
+	return i64(r.u64n(u64(max)))
+}
+
+// r.int_in_range(min, max) returns a pseudorandom int that lies in [min, max)
+[inline]
+pub fn (r SysRNG) int_in_range(min int, max int) int {
+	if max <= min {
+		eprintln('max must be greater than min')
+		exit(1)
+	}
+	// This supports negative ranges like [-10, -5) because the difference is positive
+	return min + r.intn(max - min)
+}
+
+// r.i64_in_range(min, max) returns a pseudorandom i64 that lies in [min, max)
+[inline]
+pub fn (r SysRNG) i64_in_range(min i64, max i64) i64 {
+	if max <= min {
+		eprintln('max must be greater than min')
+		exit(1)
+	}
+	return min + r.i64n(max - min)
+}
+
+// r.f32() returns a pseudorandom f32 value between 0.0 (inclusive) and 1.0 (exclusive) i.e [0, 1)
+[inline]
+pub fn (r SysRNG) f32() f32 {
+	return f32(r.u32()) / constants.max_u32_as_f32
+}
+
+// r.f64() returns a pseudorandom f64 value between 0.0 (inclusive) and 1.0 (exclusive) i.e [0, 1)
+[inline]
+pub fn (r SysRNG) f64() f64 {
+	return f64(r.u64()) / constants.max_u64_as_f64
+}
+
+// r.f32n() returns a pseudorandom f32 value in [0, max)
+[inline]
+pub fn (r SysRNG) f32n(max f32) f32 {
+	if max <= 0 {
+		eprintln('max has to be positive.')
+		exit(1)
+	}
+	return r.f32() * max
+}
+
+// r.f64n() returns a pseudorandom f64 value in [0, max)
+[inline]
+pub fn (r SysRNG) f64n(max f64) f64 {
+	if max <= 0 {
+		eprintln('max has to be positive.')
+		exit(1)
+	}
+	return r.f64() * max
+}
+
+// r.f32_in_range(min, max) returns a pseudorandom f32 that lies in [min, max)
+[inline]
+pub fn (r SysRNG) f32_in_range(min f32, max f32) f32 {
+	if max <= min {
+		eprintln('max must be greater than min')
+		exit(1)
+	}
+	return min + r.f32n(max - min)
+}
+
+// r.i64_in_range(min, max) returns a pseudorandom i64 that lies in [min, max)
+[inline]
+pub fn (r SysRNG) f64_in_range(min f64, max f64) f64 {
+	if max <= min {
+		eprintln('max must be greater than min')
+		exit(1)
+	}
+	return min + r.f64n(max - min)
+}